Prognostic impact of endoscopic response evaluation after neoadjuvant chemotherapy for esophageal squamous cell carcinoma: a nationwide validation study

Background: Our previous study reported the prognostic significance of endoscopic response (ER) evaluation, defined ER, and revealed ER as an independent prognostic factor of overall survival (OS) and recurrence-free survival (RFS) for esophageal squamous cell carcinoma (ESCC) treated with neoadjuvant chemotherapy (NAC) and surgery. The present study aimed to validate the prognostic impact of ER using a nationwide database from the authorized institute for board-certified esophageal surgeons by the Japan Esophageal Society. Methods: This study retrospectively reviewed patients with ESCC who underwent subtotal esophagectomy at 85 authorized institutes for esophageal cancer from 2010 to 2015. Patients were classified as ER when the tumor size was markedly reduced post-NAC compared to pre-NAC. The correlation between OS and RFS was investigated. Results: Of 4781 patients initially enrolled, 3636 were selected for subsequent analysis. Of them, 642 (17.7%) patients were classified as the ER group. Patients with ER showed significantly better OS and RFS. Subgroup analysis revealed the statistical difference in OS and RFS in cStage II and III, while the magnitude of survival difference between ER and non-ER was not evident in cStage I and IV. The percentage of ER varied from 46 to 87% among groups when institutions were classified into 3 subgroups based on the hospital volume, which would indicate the interinstitutional inconsistency. Conclusions: The prognostic impact of ER was validated using a nationwide database. Standardization of ER evaluation is required to improve the interinstitutional consistency and clinical validity of the ER evaluation.